Exisitng synthetic aperture radar image formation systems and techniques are complex and computationally demanding. Range migration algorithm (RMA) methods require a straight and level flight path of the aircraft. Although aircraft path compensation to the first order is commonly built into the algorithm, image distortion may still be present at both ends of the range swath when the flight path deviates from certain bound. A second issue associated with RMA is that motion compensation becomes very computational demanding for a SAR system employing a wide beam in both elevation and azimuth, such as in ground penetration radar.
Polar format (PF) algorithm methods can tolerate more flight path turbulence by performing motion compensation repeatedly on a large number of image patches. However, since the wave front for the radar pulses follows an arc instead of a straight line its tomography-type processing leads to geometric distortion and phase distortion. Consequently, pixel phase continuity only presents within each small image patch. This greatly reduces its capability in coherent change detection (CCD). In addition, a close range SAR requires many image patches in Polar Format which makes the processing very inefficient.
In radar signal processing, both RMA and PF perform pulse-to-pulse processing during the initial data collection phase. The processing along the azimuth dimension is held until pulses equivalent to the full synthetic aperture have been acquired. This tends to leave a much higher computation load during batch processing. Consequently, it requires a processor with a relatively high computation throughput rate. For RMA, it requires a large memory buffer to store the range compressed data. Then, there is a need to perform a data corner turning process in order to access data in the azimuth direction. These demand a large size memory and fast I/O bandwidth from the processor.